The Isolation Capability of a Salt Dome Utilized for High-Level Waste Disposal
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E ISOLATION CAPABILITY OF A SALT DOME UTILIZED FOR HIGH-LEVEL WASTE DISPOSAL J. HAMSTRA Netherlands Energy Research Foundation, The Netherlands.
P.O.
Box 1, 1755 ZG Petten N.H.,
INTRODUCTION The overall objective of disposal of high-level and alpha bearing wastes in deep geologic formations is
to isolate these wastes from the biosphere for such
a period of time that a subsequent future release of radionuclides from the buried wastes will not result in undue radiation exposures to man. An effective long-term isolation of radioactive waste can, because of its time scale,
never be demonstrated.
concept can only be predicted,
The performance of an underground disposal
by evaluating and analysing the performance of
the overall system of man-made and natural barriers. Model calculations can be used to perform these assessments.
Up till
most modelling was done for generic hostrock specific approaches.
now
There are
basic differences in approach to achieve the required isolation of the wastes in
the distinct hostrocks under consideration.
rive from differences in rock characteristics,
The diversities mainly dein geohydrology and in response
to emplacement of the heat producing waste. Crystalline rock has negligible plasticity. It
thereforacan develop fractures
that contain groundwater at the depth considered appropriate for disposal of high-level waste. therefore is
The isolation of the waste in a crystalline rock repository
assured by assigning an important barrier function to the waste
form, the waste container wall and a buffer material directly around the emplaced waste containers. Safety Project (KBS)
The disposal concept developed by the Nuclear Fuel
for determining the suitability of Swedish bedrock for
final storage of high-level waste is
a good example of such a multi-barrier
disposal system that relies heavily on the man-made barriers. Rock salt on the contrary can, because of its
plastic properties,
be
utilized as a potential host rock in such a way that its function as a natural barrier becomes dominant in and more in
the overall disposal concept.
It
is
this rock salt
particular this salt dome specific potential that will be discussed
in this presentation.
420 In spite of its
solubility in groundwater,
favourable host rock, -
rock salt is
considered to be a
because of
its availability in large underground structures,
- its viscoplastic properties
that makes it
such as salt domes,
essentially impermeable to liquids
and gases, - its compressive strength that in spite of its
plasticity allows for excava-
tions up to greater depths to remain accessible for disposal operations, - the ease with which it It
and
can be mined at relatively low costs.
should be recognized
that the size,
shape and internal structure of a
salt dome will vary considerably from salt dome to salt dome. internal structure of a salt dome is
a matter of concern,
The complex
because the location
of the disposal area inside the salt dome needs to be adapted to an eventual presence there
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